[brownbear]

compression ratio is different.

I'll call BS on that.

That would be a bad call.

https://www.cummins.com/engines/cummins-67l-turbo-diesel-2019

 

[brownbear]

It doesn't say anywhere the compression ratio changed.

It most certainly does. It's under "specifications."

HO - w/ Aisin SO – w/ 68RFE Auto
Horsepower 400 370
Torque 1000 850
Displacement 6.7L 6.7L
Number Of Cylinders 6 6
Bore 107 mm (4.21 in) 107 mm (4.21 in)
Stroke 124 mm (4.88 in) 124 mm (4.88 in)
Compression Ratio 16.2 :1 19 :1
Engine Wet Weight 1060 lbs 1060 lbs
Fuel System Bosch HPCR Bosch HPCR

 

[brownbear]

If I recall correctly, doesn’t the HO get the new CGI block whereas the SO truck gets the traditional engine?


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No, they're the same block. I'm wondering if the heads are set up differently which would account for the compression difference.